path: root/fs/afs/write.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* handling of writes to regular files and writing back to the server
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/backing-dev.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/netfs.h>
#include "internal.h"

static void afs_write_to_cache(struct afs_vnode *vnode, loff_t start, size_t len,
			       loff_t i_size, bool caching);

#ifdef CONFIG_AFS_FSCACHE
/*
 * Mark a page as having been made dirty and thus needing writeback.  We also
 * need to pin the cache object to write back to.
 */
bool afs_dirty_folio(struct address_space *mapping, struct folio *folio)
{
	return fscache_dirty_folio(mapping, folio,
				afs_vnode_cache(AFS_FS_I(mapping->host)));
}
static void afs_folio_start_fscache(bool caching, struct folio *folio)
{
	if (caching)
		folio_start_fscache(folio);
}
#else
static void afs_folio_start_fscache(bool caching, struct folio *folio)
{
}
#endif

/*
 * prepare to perform part of a write to a page
 */
int afs_write_begin(struct file *file, struct address_space *mapping,
		    loff_t pos, unsigned len,
		    struct page **_page, void **fsdata)
{
	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
	struct folio *folio;
	unsigned long priv;
	unsigned f, from;
	unsigned t, to;
	pgoff_t index;
	int ret;

	_enter("{%llx:%llu},%llx,%x",
	       vnode->fid.vid, vnode->fid.vnode, pos, len);

	/* Prefetch area to be written into the cache if we're caching this
	 * file.  We need to do this before we get a lock on the page in case
	 * there's more than one writer competing for the same cache block.
	 */
	ret = netfs_write_begin(&vnode->netfs, file, mapping, pos, len, &folio, fsdata);
	if (ret < 0)
		return ret;

	index = folio_index(folio);
	from = pos - index * PAGE_SIZE;
	to = from + len;

try_again:
	/* See if this page is already partially written in a way that we can
	 * merge the new write with.
	 */
	if (folio_test_private(folio)) {
		priv = (unsigned long)folio_get_private(folio);
		f = afs_folio_dirty_from(folio, priv);
		t = afs_folio_dirty_to(folio, priv);
		ASSERTCMP(f, <=, t);

		if (folio_test_writeback(folio)) {
			trace_afs_folio_dirty(vnode, tracepoint_string("alrdy"), folio);
			goto flush_conflicting_write;
		}
		/* If the file is being filled locally, allow inter-write
		 * spaces to be merged into writes.  If it's not, only write
		 * back what the user gives us.
		 */
		if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
		    (to < f || from > t))
			goto flush_conflicting_write;
	}

	*_page = folio_file_page(folio, pos / PAGE_SIZE);
	_leave(" = 0");
	return 0;

	/* The previous write and this write aren't adjacent or overlapping, so
	 * flush the page out.
	 */
flush_conflicting_write:
	_debug("flush conflict");
	ret = folio_write_one(folio);
	if (ret < 0)
		goto error;

	ret = folio_lock_killable(folio);
	if (ret < 0)
		goto error;
	goto try_again;

error:
	folio_put(folio);
	_leave(" = %d", ret);
	return ret;
}

/*
 * finalise part of a write to a page
 */
int afs_write_end(struct file *file, struct address_space *mapping,
		  loff_t pos, unsigned len, unsigned copied,
		  struct page *subpage, void *fsdata)
{
	struct folio *folio = page_folio(subpage);
	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
	unsigned long priv;
	unsigned int f, from = offset_in_folio(folio, pos);
	unsigned int t, to = from + copied;
	loff_t i_size, write_end_pos;

	_enter("{%llx:%llu},{%lx}",
	       vnode->fid.vid, vnode->fid.vnode, folio_index(folio));

	if (!folio_test_uptodate(folio)) {
		if (copied < len) {
			copied = 0;
			goto out;
		}

		folio_mark_uptodate(folio);
	}

	if (copied == 0)
		goto out;

	write_end_pos = pos + copied;

	i_size = i_size_read(&vnode->netfs.inode);
	if (write_end_pos > i_size) {
		write_seqlock(&vnode->cb_lock);
		i_size = i_size_read(&vnode->netfs.inode);
		if (write_end_pos > i_size)
			afs_set_i_size(vnode, write_end_pos);
		write_sequnlock(&vnode->cb_lock);
		fscache_update_cookie(afs_vnode_cache(vnode), NULL, &write_end_pos);
	}

	if (folio_test_private(folio)) {
		priv = (unsigned long)folio_get_private(folio);
		f = afs_folio_dirty_from(folio, priv);
		t = afs_folio_dirty_to(folio, priv);
		if (from < f)
			f = from;
		if (to >